Field of the Disclosure
The present disclosure relates to the technical field of power electronic technology, and in particularly, to a circuit and a method for overcurrent control and a power supply system including the same.
Background of the Disclosure
A power supply is used for supplying electric energy in an electronic product, which is required to meet the performance requirements of the electronic product and to protect itself from damages such as overvoltage, overcurrent and overheating. Once an electronic product fails, it will be damaged or even cause a fire or other bad consequences. Therefore, the protective function of the power supply have to be perfect, where an overcurrent protection is a common protective function.
In the prior art, as shown in FIG. 1, in a power supply system, when a short circuit of a load 107 or an overcurrent occurs at an output, the system generates a short-circuit signal SHORT by use of a shorted-output detecting circuit 106. Under the short circuit or the overcurrent, in one case, the system provides a maximum current at the output, or in another case, it provides the maximum current at the output just for a while, and then stops the output for a time period, and then provides the maximum current at the output again for some time, and then stops the output again for another time period. At this time, the voltage VFB of feedback output terminal is smaller than its reference voltage VREF, so the operational amplifier 103 remains outputting a highest value. When the maximum current is being provided at the output, the short circuit of the load 107 or the overcurrent will be recovered, the output voltage of the operational amplifier 103 will output a high-level voltage which will make an output voltage of the system rapidly increase, and when the increasing of the output voltage Vout makes the feedback signal VFB of the output voltage equal to the reference voltage VREF, the operational amplifier 103 outputs a much higher voltage than the voltage output by the operational amplifier under a steady state.
Generally, there is a capacitive element or a capacitive parameter in a regulating system, so the operational amplifier 103 needs a period of time to adjust its output voltage to a steady value. The adjusting process will cause an overshoot on the output voltage, shown in FIG. 2. The overshoot situation will cause huge damages to both of the load and the circuit of the power source.